Toxic effects metal pollutants

The mobility of arsenic compounds in soils is affected by sorp-tion/desorption on/from soil components or co-precipitation with metal ions. The importance of oxides (mainly Fe-oxides) in controlling the mobility and concentration of arsenic in natural environments has been studied for a long time (Livesey and Huang 1981 Frankenberger 2002 and references there in Smedley and Kinniburgh 2002). Because the elements which correlate best with arsenic in soils and sediments are iron, aluminum and manganese, the use of Fe salts (as well as Al and Mn salts) is a common practice in water treatment for the removal of arsenic. The coprecipitation of arsenic with ferric or aluminum hydroxide has been a practical and effective technique to remove this toxic element from polluted waters... 

Some toxic effects of heavy metals pertain to a change of amino acid contents in urine. It is established that accumulation of metals in hair and nails and secretions through urine and saliva are definitely correlated. It was obviously due to enzyme features as well as the level of environmental pollution. 

Thus the total soil pollution was connected with a respiratory system and a digestive tract. Both systems were also sensitive to such urban pollutants as heavy metals and PAH. For radionuclides the correlation with the given nosologies was not revealed. The asthma morbidity was mostly connected with soil pollution rates. This circumstance, apparently, can be related to nonspecific action of pollutants on a human organism, because the etiology of asthma is connected with the human immune defense system and allergy state (Roite, 1991). The last was shown for pesticides (Nikolaev et al., 1988) and heavy metals (Drouet et al., 1990). The sensitized immune system is, apparently, responsible for chronic toxic effects of other pollutants at low doses (Sidorenko et al., 1991 Novak and Magnussen, 1993). 

There is an abundant research on the interactions of HIOCs and metals with biological interphases, in which organic chemicals and metals are treated independently. However, few studies have considered the role of combinations of HIOCs with metals. There is a particular lack of mechanistic approaches. With regard to the metals, the FIAM has been very successful, but it remains to be shown under which conditions additional interactions, such as partitioning of hydrophobic complexes and uptake of specific complexes, are important for metal uptake and toxic effects. In particular, the role of hydrophobic complexes with both natural and pollutant compounds in natural waters has not yet been fully elucidated, since neither their abundance nor their behaviour at biological interphases are known in detail. 

The trace metals listed in Table 11.2 (with the inclusion of Sn) are of particular concern as they are toxic at low concentrations. For historical reasons, these elements are commonly referred to as the heavy metals. The degree to which the heavy metals cause toxic effects is dependent on their concentration, chemical speciation, and other environmental conditions, such as temperature. As illustrated in Table 28.6, the type and physiological state of the target organism are also important as these fectors determine the degree to which internal metabolic processes can detoxify or eliminate the pollutant. 

A number of other metals, such as iron and tin. enter into insecticide and peslicide compounds, but as purl of an urganic chemical stniciurc. us exemplified by triphenyltin hydroxide. Such compounds arc sometimes referred lo as organometallics (or, specifically in Ihc case of tin. as orgamilins). Mercury compounds are rapidly being phased out because of their long-term toxic residual effects as pollutants, particularly of fresh and saline waters. Regulations vary I mm one country to another. 

Chemometric studies indicated a lack of correlation between individual chemical parameters and estimated toxicity parameters. A significant aspect of the toxicity effect is the bioavailability form in which a pollutant is present in the analyzed sample. Efforts were made to find a link between the toxicity of a sediment sample and the mobility of the heavy metal forms it contained, but no relationship could be found between the determined toxicity and the potential toxicity, the latter calculated on the basis of the load of mobile forms of metals. A relationship was found, however, between the determined toxicity effects using the crustacean Heterocypris incongruens and the potential toxicity resulting from total metal loads. These results indicate that forms of heavy metals that are insoluble in water may nonetheless be available to H. incongruens. 

Currentiy, trace metal pollution is not a problem in the Amazon River, with the exception perhaps of localized small-scale occurrences. However, the basin includes several sites of elevated metal releases linked to gold and manganese ore mining and industrial discharges from the large cities. Seyler and Boaventura discuss the likelihood of contamination from these sources. Moreover, they come to the provocative conclusion that elevated fluxes of manganese, copper, vanadium, arsenic, and nickel may already be detectable at the river s mouth due to anthropogenic activities in the basin. Possible metal contamination should be taken seriously in the Amazon, as even small amounts of the more toxic metals may lead to widespread adverse effects in the river s aquatic systems. 

Insects and earthworms have a more intimate contact with soil pollutants and generally serve a more useful function in soil fertility. Earthworms have proven to be an easy species to study with regard to soil-polluting effects. Lead, cadmium, and copper are readily absorbed by earthworms. In high concentrations, these heavy metals are lethal. In lower concentrations, they accumulate, causing toxic effects that are manifest in reduced activity by the earthworms. 1415 ... 

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